Rotary water sprinklers are known having a drive for rotating the sprinkler about an axis that is substantially vertical when the sprinkler is installed in its usual upright orientation. This type of sprinkler includes at least one nozzle that throws a stream of water as opposed to a spray or mist. The nozzle is set in one side of the sprinkler and is usually inclined upwardly relative to the surface to be watered. Thus, as the sprinkler rotates about a vertical axis, the water stream is thrown to one side of the sprinkler and rotates with the sprinkler to water an arc segment determined by the angular extent of the sprinkler's rotation.
One problem with this type of sprinkler is getting the water in the water stream to fall or precipitate out in areas close to the sprinkler. Typically, if water is thrown in a coherent stream at some trajectory relative to the surface to be watered, the stream will tend to water a doughnut shaped ring around the sprinkler with little water being deposited close to the sprinkler. This is obviously a disadvantage since the vegetation close to the sprinkler will be underwatered. One could perhaps compensate for this by increasing the length of time the sprinkler is allowed to run. However, this increases water usage and also means that the vegetation farther from the sprinkler in the radially outer portions of the pattern will then be overwatered if the vegetation close to the sprinkler is properly watered.
Some sprinklers use multiple nozzle passages in an attempt to solve this problem. These sprinklers have a first long range nozzle passage for watering radially outer portions of the pattern and a second short range nozzle passage for watering radially inner portions of the pattern. The long range nozzle passage is often larger in diameter and may be set at a higher trajectory angle than the short range nozzle passage. U.S. Pat. No. 3,645,451 to Hauser shows a rotary sprinkler with a long range/short range nozzle passage configuration of this type.
Unfortunately, even if one uses a short range nozzle passage, one must still get the water to evenly fall or precipitate out of the water stream being ejected by that nozzle passage to evenly water the radially inner portions of the pattern. Thus, the problem described above, namely of underwatering those areas closest to the sprinkler, still exists with respect to a short range nozzle passage. Moreover, one cannot simply unduly lower the trajectory of the short range nozzle passage to point it at areas adjacent the ground as the short range nozzle passage is also responsible for watering some of the intermediate portions of the pattern as well as the areas closest to the sprinkler. In addition, pointing a nozzle passage directly at the ground is not desirable since the water stream could impact the ground with too much force, thus damaging or destroying the turf or vegetation which it was designed to water.
The long range/short range nozzle passage combination described above has been further refined by attempting to break up the water flowing in the short range nozzle passage. U.S. Pat. No. 3,794,245 to Wilson shows an upwardly extending finger placed adjacent the outlet of the short range nozzle passage for moderately breaking up the water exiting from the short range nozzle passage "for providing water delivery to the ground areas close to (the sprinkler) head". Similarly, U.S. Pat. No. 5,104,045 shows various ways of attempting to get close in coverage by a nozzle passage by deflecting the short range nozzle stream and impacting such deflected stream against various surfaces, or by impacting multiple short range nozzle streams with one another.
While breaking up the water flowing in a short range nozzle passage may improve water distribution close to the sprinkler, it creates other problems. For example, when medium to high water pressure, e.g. in the range of 50-80 psi, is sent through a nozzle, impacting water at this pressure against a break up finger or against a surface will often change much, if not all, of the stream to a spray or mist. The stream is no longer in substantially droplet form. A spray or mist is easily blown by the wind so that it may never reach the areas close to the sprinkler. Thus, at higher water pressures, those nozzles attempting to break up the water intended to reach close to the sprinkler end up also creating an undesirable spray or mist rather than having the water precipitate or fall out of the stream in droplet form.